Environmental Engineering Reference
In-Depth Information
less important than the higher yields. A tonne of U.S.
wheat needed 137 h of labor in 1800, 56 h in 1880,
and less than 1.67 h in the late 1990s. And in just two
generations, between 1940 and 1980, the labor needs
for the U.S. corn were reduced from 32 h/t to 2 h/t.
Every affluent country had experienced a massive release
of farm labor. The U.S. share went from about 64% of
total labor force in 1850 to less than 2% by the year
2000, and the same process is now underway in the
world's two most populous countries, China and India.
But a frequently quoted increase in numbers of people
supported by one U.S. farm worker—from just 4.7 in
1850 to 8 in 1900, 16 in 1950, and 95 in the year
2000—is both an underestimate and an overestimate. It
is an underestimate because large shares of U.S. planted
land have been devoted to export crops, and an overesti-
mate because a proper account would have to include
workers employed in the production of industrial inputs
as well as in the provision of support services (education,
research, extension). Such a tally could nearly double
U.S. ''agricultural'' employment, but it would still repre-
sent only about 4% of the country's labor force.
Comparisons of national accounts of energy subsi-
dies in agriculture are complicated by nonuniform analyt-
ical boundaries, choice of energy equivalents for major
inputs, selection of farmland totals, and imports of animal
feed that may originate in a number of countries on
different continents and that dominate the feedstuff con-
sumption in some countries. These realities make accu-
rate energy accounts unlikely. Good arguments can be
made for dividing the inputs by the total area involved
in agriculture or by only the land under annual or perma-
nent crops. A case-by-case approach is perhaps best.
Where grazing contributes little food, the average energy
subsidy can be calculated only for the cultivated area, but
elsewhere any managed pastures should be included in
the total.
The different results for low-subsidy, extensive field
farming and grazing in Australia or New Zealand (2-3
GJ/ha) and high-input, intensive agricultures in the
Netherlands or Israel (70-80 GJ/ha) are not surprising.
The most noteworthy finding is that China, the world's
most populous nation, is subsidizing its farming with
intensities surpassing those of the most productive North
American and European agricultures. This finding is
somewhat counterintuitive; one would expect the use of
much more labor or organic fertilizer. But China's high
fossil fuel and electricity subsidies are understandable in
view of high cropping ratios (1.5 crops/ha annually), ex-
tensive irrigation (50% of all farmland), and intensive fer-
tilization. In the late 1960s North America applied about
30 kg N/ha, and China about 5 kg N/ha. In 2005 the
respective means were about 60 kg N/ha and 165 kg
N/ha. Fertilizer nitrogen provides about 60% of the nu-
trient in China's cropping, and since over 80% of the
country's protein is derived from crops, roughly half
of all nitrogen in China's food comes from inorganic
fertilizers.
China's population thus depends for survival on exter-
nal energy subsidies, whereas the U.S. population—with
less meaty diets and a much larger agricultural labor
force—could be fed from the abundant farmland without
any synthetic fertilizers. Detailed accounts of the global
nitrogen cycle of the late 1990s indicate that about 75%
of all nitrogen in food proteins available for human con-
sumption came from arable land (the rest from pastures
and aquatic species). Because synthetic fertilizers provide
about 50% of all nitrogen in harvested crops, at least
every third person, and more likely two people out of
five, gets protein thanks to Haber-Bosch synthesis. But
